2003 Chevrolet Trailblazer, Changing the Rear Mode Actuator

This 2003 Chevrolet Trailblazer had a loud ticking noise coming from the rear of the vehicle on the passenger side. In the last post I showed how to remove the trim panels and locate the faulty actuator assembly. Please click here to see that part of this repair.

Once the trim panels were removed it was just a matter of feeling the clicking in the actuator.

The thumb latch has to be depressed to release the harness connector.

There are a total of three phillips headed screws that hold the actuator in place.

It took a little bit of wiggling around but the actuator pulls straight up off of the mode door shaft. The old actuator had several part numbers on it; 47210105, 0297707 and AH24102002. If you want to purchase the most up to date replacement actuators please click here.

I manually turned the shaft to make sure the door moved freely.

Notice the shaft has a half round section with a perpendicular tab to one side. There is a matching recess in the actuator assembly.

When voltage testing, I use an angled pick to probe the harness wires individually. I then clip my meters test lead to the pick.

There are various designs and many are useful for this kind of testing.

Now that the actuator has been replaced the system should be recalibrated. The standard Trailblazer or Envoy would need the driver’s side rear seat cushion lifted to access the fuse box. The vehicle is an EXT version and the whole seat flips up to access the interior fuse box.

There are two push pin retainers that have to be removed as shown below.

I had to locate the fuse labeled “HVAC B” on the fuse box legend.

I had to orient the legend to align the picture with the actual fuse box components.

Once I had located the proper fuse I removed it to start the recalibration process.

The key must be off before the fuse is removed.

Leave the fuse out for one minute.

Install the previously removed fuse.

Turn the ignition on for one minute.

Put your hands in your pockets and Do Not Touch Anything while the ignition is on.

Turn the ignition off for at least ten seconds but no more than thirty seconds.

Turn the ignition on and start the engine. Test the actuator for proper function.

17 discussions on “2003 Chevrolet Trailblazer, Changing the Rear Mode Actuator”

  1. Hello and thank you for this information it was great, I changed both actuators and calibrated them and everything was fine for about a month then they both started clicking again every time I start the car, I tried the re calibration method again but it did nothing, what might be the issue? Could both actuators be back already?

    Thank You

  2. I do not know of anything else that could cause the clicking noise. The noise is caused by a broken gear tooth that the actuator gears cannot move past. All internal to the actuator. I also agree that it is better to change both at the same time.

  3. From reading this two-part post I’m pretty sure it is the same problem with my 2003 Trailblazer EXT LTZ. When I use the second row controls to change the MODE, the clicking sound starts when on FEET and stops when on TOP or mixed TOP and FEET. (If I remember correctly). This would lead me to believe that it is indeed one of the actuators. As long as we have the fans turned off in the back or the mode is set to TOP or MIXED, there is no noise. Would there be anything else that could cause this noise? The clicking is strong enough to create a vibration you can feel with your hand from the inside OR the outside of the vehicle. I’m planning on replacing both actuators. One of the front actuators went out two years ago and we had it replaced. http://www.sparkys-answers.com/2010/12/2002-chevrolet-trailblazer-no-heat.html?showComment=1332318813482#c7727460842468663362

  4. The 03 and the 05 both use the same actuators for the rear system. One of the actuators controls temperature and the other controls the vent positions. You should be able to adjust the controls accordingly to see the actuators react to commands.

  5. i have the same issue with my 03 trailblazer. when i took the back passenger pannel off, i found 2 acuators. the one that is clicking is the one you were changing on your link. what is the other one near the floor of the back same area? should i change both? also i went to a salvage yard and found my same truck but it was an 2005 ext, mine is a ls. how do i know if those will work and if they are still good?

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